This invention relates to a system for securing interlocking tubular components together and in particular to a system for securing the separate detachable components of a canoe paddle together.
Spring-loaded button mechanisms have been used for many years to securely attach tubular components together where there is also a requirement for the components to be detached from each other following use. These mechanisms are normally contained within a first tubular component and include a spring-loaded button protruding from the main body of the first tubular component. In order to secure the two components together, the first tubular component is partly inserted into the second tubular component, which has a slightly larger diameter than the first component. As the first component partly enters the second component, the spring-loaded button on the first component is pushed down, against its spring, into the first component. The button remains depressed until such time as it reaches a hole in the second component, whereupon the button then rises under the action of the spring through the hole in the second component with the spring acting on the button in the hole, the two components cannot be disconnected or rotated relative to each other without the button again being depressed.
Although generally satisfactory, fittings of this type do not afford firm connections, as a certain amount of movement between the components is possible and increases with usage. This movement between the components is particularly unacceptable where the components are parts of a canoe paddle that can be disconnected for storage or transportation. Such paddlesxe2x80x94where the blades at either end of the paddle shaft can be removedxe2x80x94are well known and use interlocking mechanisms as described above to connect the blades to the shaft. However, the relative movement of the two components that is permitted by the known mechanism is disadvantageous in canoeing. The relative movement of the blade and shaft produces an inefficient power transmission from the canoeist through the shaft to the blades. For this reason this known locking mechanism is undesirable in applications where efficient power transmission is required.
Thus, it is an object of the present invention to provide a system for the connection of tubular components which provides a secure connection between the components and does not permit movement of those components relative to each other.
According to a first aspect of the present invention, there is provided a system comprising first and second tubular members and a locking apparatus for releasably securing the first tubular member to the second tubular member, wherein the first tubular member is resiliently expandable in diameter and has a diameter in the unexpanded state such that it can fit within the second tubular member, and wherein the first and second tubular members are provided with first and second apertures, respectively, in the wall of the respective tubular member,
wherein the locking apparatus is located within the first tubular member and comprises:
first and second clamping members adapted to apply a clamping force to opposite internal faces of the first tubular member in a clamping direction;
an adjustment means provided between the first and second clamping members for adjusting the clamping force applied by the clamping members; and
a resiliently mounted detent member mounted within the first clamping member adapted to engage with the first and second apertures when the first and second apertures are mutually aligned, wherein the spring-loaded button member has a passage extending therethrough to permit access to the adjustment means.
Preferably, the first clamping member has an internal thread, and the adjustment means comprises an externally threaded member that engages with the internal thread of the first clamping member.
Preferably, the adjustment means is adapted such that rotation of the externally threaded member causes the first and second clamping members to move apart and thereby apply a clamping force.
Preferably, the externally threaded member is a screw member. Preferably, the externally threaded member has a drivable head orientated towards the first and second apertures. Preferably, the drivable head has a hexagonal socket for driving by an Allen key.
Preferably, the resiliently mounted detent member comprises a button portion which can pass through the mutually aligned first and second apertures and a shoulder portion which abuts against the inner surface of the first tubular member, and the resiliently mounted detent member comprises a helical spring acting between the button portion and first clamping member.
Preferably, the first and second clamping members are provided with end bearing surfaces having a shape corresponding to the internal surface of the first tubular member.
Preferably, the second clamping member has a sleeve portion which fits around a portion of the first clamping member so as to allow relative axial movement of the first and second clamping members in the clamping direction.
Preferably, the first tubular member is provided with two substantially diametrically opposed, longitudinally extending slits adapted to permit resilient deformation of the portions of the tubular member between the slits in a direction perpendicular to the plane of the slits.
Preferably, the first and second clamping members are positioned such that the clamping direction is perpendicular to the plane of the slits.
Preferably, the first and second tubular members are of composite construction. Preferably, the first and second tubular members are components of an oar or paddle.
According to a second aspect of the present invention, there is provided a method of releasably interconnecting first and second tubular members so as to provide a rigid joint, wherein the first tubular member is resiliently expandable in diameter and has a diameter in the unexpanded state such that it can fit within the second tubular member, the first and second tubular members being provided with first and second apertures, respectively, in the wall of the respective tubular member, a resiliently mounted detent member being mounted with the first clamping member and engaging the first and second apertures when the first and second apertures are mutually aligned, and wherein first and second clamping members are provided within the first tubular member,
the method comprising the steps of:
engaging the resilently mounted detent member in the mutually aligned first and second apertures so that the first and second tubular members are loosely connected; and
adjusting the first and second clamping members so as to provide a clamping force which clamps the external surface of the first tubular member against the internal surface of the second tubular member so that the first and second tubular members are rigidly connected.
Preferably, the first and second clamping members are adjusted by means of a screw adjustment.
Preferably, the resiliently mounted detent member has a passage extending therethrough and the screw adjustment is carried out by inserting a tool through the passage to the first and second clamping members. Preferably, the screw adjustment in carried out by rotating a threaded member which acts to move the first and second clamping members apart. Preferably, the threaded member is a bolt or screw.
Preferably, the threaded member has a drivable head orientated towards the first and second apertures. Preferably, the drivable head has a hexagonal socket for driving by an Allen key.